Conventionally, there are known techniques for enlarging or reducing (zoom-in and out) a display image by a player holding and moving an operation device. For example, in an image processing apparatus of Document 1 below, when a player moves a controller (operation device) back and forth with respect to an image display device while pressing a predetermined button of the controller, the moving distance and the like of the controller are calculated. Then, enlargement/reduction of a display image is performed in accordance with the calculated moving distance and the like. Document 1: Japanese Laid-Open Patent Publication No. 2007-236697
Also, for example, in an archery video game of Document 2 below, a player moves a controller (operation device) backward while pressing a predetermined button thereof, with the front surface of the controller facing a display image. When the player aims at a target by adjusting the direction of the controller and then releases the predetermined button that has been pressed, an arrow is shot. Document 2: “Nintendo authorized guidebook, Mario and Sonic at Beijing Olympics (Wii version)” Shogakukan, Feb. 2, 2008, pp. 66-67.
Also, for example, in a video game of Document 3 below, when a player moves a controller (operation device) toward an image display device while pressing an A button of the controller, a display image is enlarged. When the player presses a B button in this state, an action of firing a gun at an aim pointed by the controller is performed. In this manner, the technique of Document 3 allows the player to enlarge the display image and to perform an attack action by operating the controller. Document 3: “Red Steel operation manual”, RVL-REDJ-JPN, UBISOFT, Dec. 2, 2006, P 18 (firing a gun), P 20 (zoom-in).
However, the above techniques involve the following problems.
The technique of Document 1 allows enlargement/reduction of an image. However, in order to cancel the enlargement/reduction of the image that has been performed and to cause the enlarged/reduced image to return to its original size, the player needs to move the controller to a reverse direction. This tends to result in onerous operations for the player.
In the video game of Document 2, when the player moves the controller backward while pressing the predetermined button thereof, a target appears in the display image. However, the display image is not enlarged. This results in a relatively less realistic feeling of aiming at the target.
In the video game of Document 3, the player can perform an attack action while zooming-in, and therefore, can aim at the target easily. However, since the zoom-in motion and the attack action are realized by independent operations, respectively, the player needs to perform the zoom-in operation and the canceling operation of the zoomed-in state separately. Therefore, in such a case where the player wants to cancel the zoom quickly and perform the next attack, the operations tend to be onerous for the player.